Applying the generalized eigenvalue method to extract masses and decay constants in the D_s-meson system

We discuss the application of the generalized eigenvalue problem to lattice QCD determinations of energies and matrix elements in the pseudoscalar and vector meson channel of the charm-strange meson system. The computations employ CLS N_f = 2 ensembles with the Wilson gauge action, O(a) improved Wilson-clover fermions and lattice spacings of about 0.065 and 0.05 fm. To extract the ground state masses and decay constants and to investigate effects from excited states, our analysis involves enlarged bases of interpolating fields, e.g., matrices of cross correlators defined via different iterations of Gaussian smearing or including terms with covariant derivatives. These techniques are also expected to be useful for studies of the phenomenologically interesting charmonium system.